Tubing



Oct. 13, 1931. H. w. BUND'Y TUBING Filed NOV. 18, 1927 A TTORNE Y.

Patented Oct. 13, 1931 UNITED- STATES PATENT OFFICE HARRY W. BUNDY, OF DETROIT, MICHIGAN, ASSIGNOR, BY MESN'E ASSIGNMENTS, TO

BUNDY TUBING COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHI- GAN TUBING Application filed November 18, 1927. Serial No. 234,088.

6 of an inch in thickness of the walls. This is necessary in order to permit the bending of the tube on the radius employed in the average water heater.

It is the object of my invention to provlde a tube which can be made of relatively thin stock, and which at the same time has a flexibility which will permit the tube to be bent on a relatively small radius. This will permit water heater tubes to be made of much lighter stock, and results in considerable saving in copper or other metal.

In the drawings:

Fig. 1 shows a water heater employing my improved tubing.

Fig. 2 is a view partly in section, showing one form of the tube. Fig. 3 is a similar view, showing a different form of the tube.

Figs. 4 to 7 inclusive are sections showing different forms that the interior tube may ta e.

- a designates an interior tube which maybe fashioned in any one of the several present day production methods, as, for instance, with a lock-seam 1), shown in Fig. 5, the tube being rolled or drawn through dies in the form of a strip and made in continuous lengths of lock seam. In Fig. 6 the so-called Bundy tube is used, being a two-ply tube. Such a tube is shown in my Patent No. 1,431,368 of October 10, 1922. Fig. 7 is a form of lap-seam tube, and Fig. is a form of seamless, welded,

' or brazed tube.

The point is that the interior tube is a piece of longitudinally fashioned tube,-that iS, tube fashioned into shape while traveling longitudinally either by dies, rolls, rolls and dies, or by the piercing operation used in making seamless tube, and I then drawing it down to size. Welded and brazed tube is also longitudinally fashioned.

on the outside of the inner tube, I wind a close helix, or what is sometimes called a spiral. This gives the interior tube, which is made of thin stock, say .010 to .015 inch, great strength against bursting strains by reason of interposing the lengthwise strength of the outer tube stock to expanding strains on the inner tube. The result is that the outer tube stock may also be relatively thin, from .010 to .015 of; an inch. At the same time the outside helix permits great flexibility in this thin tube in bending.

In Fig. '2 the outside helix is wound in abutting relation. In Fig. 3 the outside helix is wound with a slight overlap. The helix may or may not be soldered or brazed to the under tube. It is possible to wind the helix on very tightly, so'that it will cling and take aseat on the inner tube. This arrangement is of course more flexible than the helix that is soldered or brazed in place.

It will be apparent that the tube may be of terial.

What I claim is 1. As a new article of manufacture, a coil bent on a relatively small radius, comprising a thin walled longitudinally fashioned tube of non-corrodible metal covered by a thin strip of metal wound as a helix on said tube with the edges of adjacent convolutions of the helix in substantially abutting relation.

2. As a new article of manufacture, a coil comprising a longitudinally fashioned-tube of copper stock approximating .010 to .015 of an inch in thickness covered by a strip of copper, brass, steel or any other suitable mametal wound as a helix upon said tube approximating .010 to .015 of an inch in thickness with the edges of adjacent convolutions in substantial abutting relation.

3. A tubefor a water heater coil or the like, comprising an inner tubular body of relatively thin copper stock which has substantially sufficient strength to withstand the lapse if bent thin walls which would colas required, as compared to walls of a conventional single ply tube for such a coil or the like, which are thick enough to prevent such collapse, and an exterior tube formed by metal stock of ribbon form wound helically upon the inner tube with adjacent convolutions in substantial abutting relation which reinforces the inner tube and permits it to be bent without collapsing, the walls of the composite tube consisting of the combined inner and outer tube walls having a thickness which is less than the thickness of the walls of the above mentioned conventional single ply tube.

In testimony whereof I have aflixed my signature.

HARRY W. BUNDY.

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